1. Field of the Invention
The present invention relates to a method and apparatus for transferring heat within diverse user environments, using centrifugal forces to realize the evaporator and condenser functions required in a vapor-compression type heat transfer cycle.
2. Brief Description of the State of the Prior Art
For more than a century, man has used various techniques for transferring heat between spaced apart locations for both heating and cooling purposes. One major heat transfer technique is based on the reversible adiabatic heat transfer cycle. In essence, this cycle is based on the well known principle, in which energy, in the form of heat, can be carried from one location at a first temperature, to another location at a second temperature. This process can be achieved by using the heat energy to change the state of matter of a carrier fluid, such as a refrigerant, from one state to another state in order to absorb the heat energy at the first location, and to release the absorbed heat energy at the second location by transforming the state of the carrier fluid back to its original state. By using the reversible heat transfer cycle, it is possible to construct various types of machines for both heating and/or cooling functions.
Most conventional air conditioning systems in commercial operation use the reversible heat transfer cycle, described above. In general, air conditioning systems transfer heat from one environment (i.e. an indoor room) to another environment (i.e. the outdoors) by cyclically transforming the state of a refrigerant (i.e. working fluid) while it is being circulated throughout the system. Typically, the state transformation of the refrigerant is carried out in accordance with a vapor-compression refrigeration cycle, which is an instance of the more generally known "reversible adiabatic heat transfer cycle".
According to the vapor-compression refrigeration cycle, the refrigerant in its saturated vapor state enters a compressor and undergoes a reversible adiabatic compression. The refrigerant then enters a condenser, wherein heat is liberated to its environment causing the refrigerant to transform into its saturated liquid state while being maintained at a substantially constant pressure. Leaving the condenser in its saturated liquid state, the refrigerant passes through a throttling (i.e. metering) device, wherein the refrigerant undergoes adiabatic throttling. Thereafter, the refrigerant enters the evaporator and absorbs heat from its environment, causing the refrigerant to transform into its vapor state while being maintained at a substantially constant pressure. Consequently, as a liquid or gas, such as air, is passed over the evaporator during the evaporation process, the air is cooled. In practice, the vapor-compression refrigeration cycle deviates from the ideal cycle described above due primarily to the pressure drops associated with refrigeration flow and heat transfer to or from the ambient surroundings.
A number of working fluids (i.e. refrigerants) can be used with the vapor-compression refrigeration cycle described above. Ammonia and sulfur dioxide were important refrigerants in the early days of vapor-compression refrigeration. In the contemporary period, azeotropic refrigerants, such as R-500 and R-502, are more commonly used. Halocarbon refrigerants originate from hydrocarbons and include ethane, propane, butane, methane, and others. While it is a common practice to blend together three or more halogenated hydrocarbon refrigerants such as R-22, R125, and R-290, near-azeotropic blend refrigerants suffer from temperature drift. Also, near azeotropic blend refrigerants are prone to fractionation, or chemical separation. Hydrocarbon based fluids containing hydrogen and carbon are generally flammable and therefore are poorly suited for use as refrigerants. While halogenated hydrocarbons are nonflammable, they do contain chlorine, fluorine, and bromine, and thus are hazardous to human health.
Presently, the main refrigerants in use are the halogenated hydrocarbons, e.g. dichlorodifluoromethane (CCL2F2), commonly known as R-12 refrigerant. Generally, there are three groups of useful hydrocarbon refrigerants: chlorofluorocarbons, (CFCs), hydrochlorofluorocarbons, (HCFCs), which are created by substituting some or all of the hydrogen with halogen in the base molecule. Hydrofluorocarbons, (HFCs), contain hydrogen, fluorine, and carbon. However, as a result of the Montreal Protocol, CFCs and HCFCs are being phased out over the coming decades in order to limit the production and release of CFC's and other ozone depleting chemicals. The damage to ozone molecules (O.sub.3) comprising the Earth's radiation-filtering ozone layer occurs when a chlorine atom attaches itself to the O.sub.3 molecule. Two oxygen atoms break away leaving two molecules. One molecule is oxygen (O.sub.2) and the other is chlorine monoxide molecule (CO). The chlorine monoxide is believed by scientists to displace the ozone normally occupying that space, and thus effectively depleting the ozone layer.
While great effort is being expended in developing new refrigerants for use with machines using the vapor-compression refrigeration cycle, such refrigerants are often unsuitable for conventional vapor-compression refrigeration units because of their incompatibility with existing lubricating additives, and the levels of toxicity which they often present. Consequently, existing vapor-compression refrigeration units are burdened with a number of disadvantages. Firstly, they require the use of a mechanical compressor which has a number of moving parts that can break down. Secondly, the working fluid must also contain oil to internally lubricate the compressor. Mineral oil has been used in refrigeration systems for many years, and alternative refrigerants like hydrofluorocarbons (HFC) require synthetic lubricants such as alkylbenzene and polyester. These use of such lubricants diminishes system efficiency. Thirdly, existing vapor-compression systems require seals to prevent the escape of harmful refrigerant vapors. These seals can harden and leak with time. Lastly, new requirements for refrigerant recovery increase the cost of a vapor-compression unit.
In 1976, Applicant disclosed a radically new type of refrigeration system in U.S. Pat. No. 3,948,061, now expired. This alternative refrigeration system design eliminated the use of a compressor in the conventional sense, and thus many of the problems associated therewith. As disclosed, this prior art system comprises a rotatable structure having a hollow shaft with a straight passage therethrough, and about which a closed fluid circuit is supported. The closed fluid circuit is realized as an assemblage of two spiral tubular assemblies, each consisting of first and second spiraled tube sections. The first and second spiraled tube sections have a different number of turns. A capillary tube, placed between the condenser and evaporator sections, functions as a throttling or metering device. When the rotatable structure is rotated in a clockwise direction, one end of the tube assembly functions as a condenser, while the other end thereof functions as an evaporator. As disclosed, means are provided for directing separate streams of gas or liquid across the condenser and evaporator assemblies for effecting heat transfer operations with the ambient environment.
In principal, the refrigeration unit design disclosed in U.S. Pat. No. 3,48,061 provides numerous advantages over existing vapor-compression refrigeration units. However, hitherto successful realization of this design has been hindered by a number of problems. In particular, the use of the capillary tube and the hollow shaft passage create imbalances in the flow of refrigerant through the closed fluid flow circuit. When the rotor structure is rotated at particular speeds, there is a tendency for the refrigerant fluid to cease flowing therethrough, causing a disturbance in the refrigeration process. Also, when using this prior art centrifugal refrigeration design, it has been difficult to replicate the refrigeration effect with reliability, and thus commercial practice of this alternative refrigeration system and process has hitherto been unrealizable.
Thus, there exists a great need in the art for an improved centrifugal heat transfer engine, which avoids the shortcomings and drawbacks thereof, and allows for the widespread application of such an alternative heat transfer technology in diverse applications.